also observed at ~290 and ~380 nm in the solid state, which correspond to characteristic π-πà transitions in the naphthyl groups of 1. The CD spectra of (S)-1 in two
states are very similar in their long-wavelength tails. In contrast to the CPL spectra,
the long-wavelength CD Cotton bands of (S)-1 were both positive (+); the g CD
values of first Cotton CD band of (S)-1 were +3.5 Â 10
–4 at λ CD ¼ 345 nm in the
PMMA film-dispersed state and +7.6 Â 10
–4 at λ CD ¼ 351 nm in the KBr pelletdispersed state. These g CD values are slightly larger than that of the CHCl 3 solution
of (S)-1 (g CD ¼ ~+2.0 Â 10
–4 ). The CD amplitudes of (S)-1 in PMMA and KBr were
evaluated as follows: g CD ¼ ((Abs(L ) À Abs(R))/|(Abs(L ) + Abs(R))/2|.
To determine the origins of the CPL and CD spectra of (S)-1 in its PMMAdispersed and KBr-dispersed states, the equilibrium structures of single molecules
of 1 in solution (or PMMA) and KBr were compared. The equilibrium dihedral angle
(θ ¼ (O)C-C-C-C(O)) of (S)-1 in CHCl 3 solution was determined to be 89.6
, while
the structure of a single (S)-1 molecule in the PMMA film-dispersed state was
identical to that in solution. X-ray crystallography revealed that the dihedral angle
θ of (S)-1 in the solid state is 117.1
. Although these angles in the two states differ,
the signs of the first Cotton CD bands of 1 in each state should be the same based on
the simulated CD spectra reported in Sect. 2.2. These results suggest that the
inversion of the CPL bands observed for 1 is determined by whether or not there
are intermolecular neighboring group effects operating between chiral binaphthyl
units in the photoexcited states.
In conclusion, the solid-state CPL of an axially chiral binaphthyl fluorophore can
be controlled by changing its external solid-state matrix environment, from a PMMA
film-dispersed state to a KBr pellet-dispersed state.
(a)
(b)
0
2
4
6
8
10
12
14
16
18
20
-200
-150
-100
-50
0
50
100
150
290 310 330 350 370 390
Absorbance
CD / mdeg
Wavelength / nm
0
0.5
1
1.5
2
2.5
3
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
290 310 330 350 370 390
Absorbance
CD / mdeg
Wavelength / nm
Fig. 2.13 CD (upper) and UV-Vis absorption (lower) spectra for (S)-1 (black) and (R)-1 (red) in (a)
the PMMA film-dispersed state and (b) the KBr pellet-dispersed state
20
Y. Imai
states are very similar in their long-wavelength tails. In contrast to the CPL spectra,
the long-wavelength CD Cotton bands of (S)-1 were both positive (+); the g CD
values of first Cotton CD band of (S)-1 were +3.5 Â 10
–4 at λ CD ¼ 345 nm in the
PMMA film-dispersed state and +7.6 Â 10
–4 at λ CD ¼ 351 nm in the KBr pelletdispersed state. These g CD values are slightly larger than that of the CHCl 3 solution
of (S)-1 (g CD ¼ ~+2.0 Â 10
–4 ). The CD amplitudes of (S)-1 in PMMA and KBr were
evaluated as follows: g CD ¼ ((Abs(L ) À Abs(R))/|(Abs(L ) + Abs(R))/2|.
To determine the origins of the CPL and CD spectra of (S)-1 in its PMMAdispersed and KBr-dispersed states, the equilibrium structures of single molecules
of 1 in solution (or PMMA) and KBr were compared. The equilibrium dihedral angle
(θ ¼ (O)C-C-C-C(O)) of (S)-1 in CHCl 3 solution was determined to be 89.6
, while
the structure of a single (S)-1 molecule in the PMMA film-dispersed state was
identical to that in solution. X-ray crystallography revealed that the dihedral angle
θ of (S)-1 in the solid state is 117.1
. Although these angles in the two states differ,
the signs of the first Cotton CD bands of 1 in each state should be the same based on
the simulated CD spectra reported in Sect. 2.2. These results suggest that the
inversion of the CPL bands observed for 1 is determined by whether or not there
are intermolecular neighboring group effects operating between chiral binaphthyl
units in the photoexcited states.
In conclusion, the solid-state CPL of an axially chiral binaphthyl fluorophore can
be controlled by changing its external solid-state matrix environment, from a PMMA
film-dispersed state to a KBr pellet-dispersed state.
(a)
(b)
0
2
4
6
8
10
12
14
16
18
20
-200
-150
-100
-50
0
50
100
150
290 310 330 350 370 390
Absorbance
CD / mdeg
Wavelength / nm
0
0.5
1
1.5
2
2.5
3
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
290 310 330 350 370 390
Absorbance
CD / mdeg
Wavelength / nm
Fig. 2.13 CD (upper) and UV-Vis absorption (lower) spectra for (S)-1 (black) and (R)-1 (red) in (a)
the PMMA film-dispersed state and (b) the KBr pellet-dispersed state
20
Y. Imai